Throttle lock-out arrangement

ABSTRACT

A carburetor assembly having primary and secondary induction passages or bores with primary and secondary throttle valves respectively situated therein and a choke valve in the inlet of the primary induction passage, has linkage means interconnecting the primary and secondary throttle shafts and valves so as to enable the opening and closing thereof in response to operator demands; additional thermostatically controlled latching means are provided so as to prevent the opening of the secondary throttle valve until the choke valve is fully opened and a predetermined engine temperature has been attained.

United States Patent Mitchell [151 3,682,149 1 Aug. 8, 1972 [54] THROTTLE LOCK-OUT ARRANGEMENT [72] Inventor: Robert D. Mitchell, 1291 Beaupre St., Madison Heights, Mich. 97521 [22] Filed: Aug. 19, 1970 [21] Appl. No.: 65,173

[52] US. Cl. ..123/119 F, 123/127, 261/23 A, 261/39 B [51] Int. Cl. ..F02m l/10, F02m 11/06 [58] Field ofSearch ..l23/l27, 119 F; 261/23 A, 39 B, 39 C [56] References Cited UNITED STATES PATENTS 2,681,213 6/1954 Gordon ..l23/l27 X 3,529,585 9/1970 Stoltman ..l23/1l9F Primary Examiner-Wendell E. Burns Attorney-Walter Potoroka, Sr.

[ ABSTRACT A carburetor assembly having primary and secondary induction passages or bores with primary and secondary throttle valves respectively situated therein and a choke valve in the inlet of the primary induction passage, has linkage means interconnecting the primary and secondary throttle shafts and valves so as to enable the opening and closing thereof in response to operator demands; additional thermostatically controlled latching means are. provided so as to prevent the opening of the secondary throttle valve until the choke valve is fully opened and a predetermined engine temperature has been attained.

10 Claims, 8 Drawing Figures PATENTEDAUG 8 I972 SHEET 1 OF 3 I NVENTOR. ame/z A I TURN? Y P'A'TEN'TEDAus 8 1922 3,682,149

sum 2 or 3 I.\'VE.\"TUR.

ATTORNEY ZJM THRO'ITLE LOCK-OUT ARRANGEMENT I BACKGROUND OF THE INVENTION Heretofore, various forms of carburetors employing primary and secondary induction passages, and corresponding throttle valves, have been proposed by the prior art. Such carburetors could be classified into two broad catagories, one comprising those carburetors egploying mechanically actuated secondary throttle v ves.

In the past it has been considered desireable to prevent the opening of the secondary throttle valves until the choke valve was first opened to a predetermined position or to a fully opened position at which time linkage means associated with the choke valve would permit the opening of the secondary throttle valves. v

1 However, a problem exists with such prior art structures in that in order to reduce the level of contaminating exhaust emission, it is desireable to have the choke valve open relatively fast but in order to provide for acceptable engine operating performance, it is desirable to prevent the secondary throttle valves from opening until an engine temperature is reached which is in excess of that temperature at which the choke valve is fully opened.

Accordingly, the invention as disclosed and described herein is primarily directed to the solution of the above as well as other related problems.

SUMMARY OF THE INVENTION According to the invention, a fuel induction device for an internal combustion engine comprises a body, primary and secondary induction passage means formed through said body, primary and secondary throttle valves respectively situated in said primary and secondary induction passages for controlling the flow of motive fluid therethrough, a choke valve pivotally mounted in the primary induction passage upstream of said primary throttle valve, first means associated with said choke valve and effective for alternately moving said choke valve to a fully closed position and to a fully opened position, second means associated with said secondary throttle valve for preventing said secondary throttle valve from being opened at least until said choke valve is fully opened, or later, and a predetermined minimum engine temperature is attained sub sequent to said choke valve being fully opened.

Various general and specific objects and advantages of the invention will become apparent when reference is made to the following detailed description of the invention considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS In the drawings, wherein certain details and elements may, for purposes of clarity, be omitted from one or more views:

FIG. 1 is a simplified representation, in perspective, (mostly used for purposes of reference) of a carburetor embodying the teachings of the invention;

FIG. 2 is an elevational view of the linkage means, carried by the carburetor, when viewed in the direction of arrow 18 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 but showing the linkages in somewhat different operating positions;

FIG. 4 is generally a plan view of the linkage means of FIGS. 2 and 3 taken generally on the plane of line 4-4 of FIG. 3 and looking in the direction of the arrows;

FIG. 5 is an elevational view of the linkage means, carried by the carburetor, when viewed in the direction of arrow 20 of FIG. 1;

FIG. 6 is generally a plan view of the linkage means of FIG. 5 taken generally on the plane of line 6-6 of FIG. 5 and looking in the direction of the arrows;

FIG. 7 is a view similar to FIG. 5 but showing the linkage means in a difierent operating position; and

FIG. 8 is a view illustrating a fragmentary portion of the linkage means of either FIGS. 2 or 3 in a different operating position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in greater detail to the drawings, FIG. 1 diagrammatically illustrates a carburetor 10 with a carburetor body 12provided with an air inlet portion 14 and a mounting flange 16 by which the carburetor assembly can be secured as to the intake manifold of an associated internal combustion engine.

FIG. 2 is an enlarged view, in elevation, of the linkage arrangement carried by the carburetor 10 when viewed in the direction of arrow 18 of FIG. 1. As indicated, the carburetor 10 is provided with primary and secondary induction passages 22 and 24 formed therethrough with primary and secondary throttle valves 26 and 28 respectively situated therein and carried by rotatable transversely extending primary and secondary throttle shafts 30 and 32. The primary induction passage means 22 may have the inlet thereof controlled as by a choke .valve 34, which may be mounted for pivotal rotation on a choke shaft 36 journalled generally as within the air inlet portion 14.

The primary throttle shaft 30 has a first lever 38 fixedly secured to the end thereof as by a suitable locking screw 40 so as to cause lever 38 to be moved in accordance with rotation of the primary throttle shaft 30. A second lever 42, having arm abutment type portions 44, 46 and 48, is situated on or about throttle shaft 30 so as to be freely rotatable with respect to the primary throttle shaft 30.

As generally shown, the transversely extending abutment arm 44 of lever 42 is generally in the path of travel of an adjustable abutment screw 50 threadably carried by a similar transversely projecting arm 52 of lever 38. Further, abutment arm 46 of lever 42 is also moveable in the general plane of the stepped surfaces 54, 56, 58 and 60 of a fast idle cam member 62, which abutment arm 48 is provided in order to, if need be, engage an abutment surface 64 on a boss 66 carried by the carburetor body 12 in order to prevent the lever 42 from accidentally rotating an excessive amount in the clockwise direction.

A third shaft 68journa1led in the carburetor body 12, generally parallel to primary throttle shaft 30, has a projecting end and a flatted portion 70 fixedly secured to a lever 72 which includes arm portions 74, 76, 78 and 80. As best seen in FIG. 4, lever arm portion 76 is bent generally outwardly (with reference to the carburetor body 12) of the main portion of lever 72 while arm portion 74 is bent generally inwardly; similarly, arm portion 78 is bent inwardly as to be extending generally in the path of possible travel of a weight member 82.

Arm portion 80 has a generally arcuate slot 84 formed therein which slideably receives therethrough one end 86 of a linkage member 88 having its other end 90 pivotally connected to a moveable outputmember 92 of a diaphragm type pressure responsive motor assembly 94 mounted to the carburetor body as by a bracket 96 and connected as by a conduit 98 to a suitable source of engine or manifold vacuum as is well known in the art.

At certain times when lever 72 is rotated counterclockwise arm 78 will engage the lower edge of weight 82 and cause the weight 82, which is freely journalled about shaft 68, to be correspondingly rotated. An abutment portion 100 carried by the carburetor body 12 serves as a positive stop limiting such counterclockwise rotation of weight member 82.

At other times when lever 72 is rotated clockwise, the inwardly bent arm portion 74 engages the lower edge of fast idle cam 62 and causes the cam 62, which is freely journalled about shaft 68, to be correspondingly rotated clockwise.

Arm portion 76 is provided with a slot 102 formed therein which slideably receives therethrough one end 104 of a linkage member 106 which has its opposite end 108 pivotally connected to an arm 110 of a lever 112 pivotally secured as by a suitable fastener 114 to a boss 116 carried by the carburetor body 12. Additionally, lever 112 has arm portion 118 and 120 of which arm 118 is a swingable actuating member and arm 120 is pivotally connected to one end of a linkage 122 operatively connected to suitable temperature responsive means 124 (best seen in FIG. 3). As best shown in FIG. 4, it can be seen that lever arm 118 is bent to be generally disposed inwardly of arm 120 while lever arm 110 is disposed outwardly of arm portion 120. v

A latching lever 126 pivotally secured, as by a pivot member 128, to a cooperating supporting boss 130 carried by the carburetor body 12 has a swingable end formed as by a transversely extending abutment arm 132 which, as shown in FIGS. 2, 3 and 4, is adapted to be at times abutably engageable by an abutment surface 134 formed on a member 136 so as to be generally eccentrically disposed with respect thereto. Member 136 is fixedly secured to the end of secondary throttle shaft 32 as by suitable locking or fastening means 138 so that rotation of the secondary throttle shaft 32 and valve 28 cannot occur without the corresponding rotation of member 136.

As previously disclosed, the weight member 82 and the fast idle cam 62 are each independently rotatable about the shaft 68; however, as best seen in FIGS. 2 and 4, the weight member 82 is provided with a first generally transversely extending arm portion 140 which is adapted to at times abut against the fixed stop 100 so as to thereby limit the counter-clockwise rotation of the weight member 82 to a maximum position as generally depicted in FIG. 2. Further, weight member 82 has a generally radial extension arm 142 which is adapted to at times abutingly engage a lateral extending arm 144 carried by the fast idle cam member 62 to follow the clockwise rotation of weight 82.

An additional lever arm 146 (FIG. 3) is suitably fixedly secured at one end thereof to shaft 68 so as to thereby experience rotation whenever shaft 68 is rotated. The other end of the lever 146 is pivotally connected to linkage means 148 which is, in turn, pivotally connected to a lever arm 150 fixedly secured to the choke shaft 36.

As is generally well known in the carburetor art, a thermostatic element such as a bimetal 152 (FIG. 3) is so situated within a suitable stove 154 as to be sensitive and responsive to engine heat. In the embodiment of the invention disclosed herein, the birnetal 152 is effective for lowering linkage 122 as engine temperature decreases and effective for raising linkage 122 as engine temperature increases.

Accordingly, when engine temperature has sufficiently decreased, bimetal 150 has caused linkage 122 to be moved downwardly, as depicted in FIG. 2, so as to cause lever 112 to be rotated clockwise about pivot 114 resulting in linkage 106 being moved a maximum distance to the right causing its end 104 to be abutingly engaged with the generally right end of slot 102 in lever 72 so as to rotate lever 72 a maximum amount in the counter-clockwise direction about the axis of shaft 68. Because of the fixed connection between shaft 68 and lever 72 and lever 146,"such rotation of lever 72 causes corresponding rotation of shaft 68 and lever 146 resulting in choke valve 34 being rotated counter-clockwise to its nominally closed position as shown in FIG. 2.

If it is assumed that immediately prior to the engine being relatively cold, as described above, the engine was relatively warm and the various levers and linkages described above were in the positions shown in FIG. 3, it can be seen that as lever 72 started to rotate counterclockwise arm portion 78 would start to lift weight member 82 causing it to rotate with lever 72 and thus permitting the fast idle cam 62 to move downwardly from its position shown in FIG. 3. However, even though lever 72 and weight 82 continue to experience rotation, such downward (counter-clockwise) movement of fast idle cam 62 becomes arrested when the swingable end thereof engages the upper end of intermediate throttle stop lever 42 which is in the general path of travel of fast idle cam 62. Accordingly, even after lever 72 reaches the position shown in FIG. 2, the fast idle cam 62 will not reach its position shown in FIG. 2 until the primary throttle shaft 30 is at least partly rotated in the throttle opening direction thereby swinging end 46 of lever 42 some distance counterclockwise and permitting cam member 62 to fall to its position shown in FIG. 2 which, at that time, is determined by the simultaneous abutting engagement between stop and abutment arm as well as between lever portion 142 and arm or projection 144.

Viewing the carburetor 10 in the direction of arrow 20 of FIG. 1, it can be seen that the opposite ends of primary and secondary throttle shafts 30 and 32 respectively have levers and 162 fixedly secured thereto. As should be apparent, rotation of shaft 30 must always be accompanied by rotation of lever 160 and rotation of shaft 32 must always be accompanied by rotation of lever 162. A first arm portion 164 of lever 162 may be provided with an aperture 166 formed therethrough for connection to suitable related actuating linkage leading as to the foot-operated throttle control within the associated vehicle as is well known in the art. Lever 160 is further provided with a generally transversely extending arm portion 168 which, as can be seen in both FIGS. 6 and 5, passes under a lever member 170.

Lever member 170 includes a generally tubular mounting portion 172 situated about the primary throttle shaft 30 in a manner permitting relative rotation therebetween. First and second arms 174 and 176 extend from the mounting portion 172 with arm 174 being operatively connected to lever 162 via an interconnecting linkage 178 which has its one end 179 pivotally connected to arm 174 and has its medial portion slideably received through a slot 180 formed in lever 162. When the secondary throttle 28 is closed, an extending leg 182 of linkage 178 passes along the opposite side of lever 162 in a manner so as to have the end 184 thereof terminate juxtaposed to and resting against an inwardly bent arm 186.

An additional lever 188 is suitably fixedly secured to primary throttle shaft 30 so as to be rotatable in unison therewith. As can be seen in both FIGS. 5 and 6, arm 190 of lever 188 is so positioned as to have end 192 thereof abutingly engageable with the end 194 of an adjustable throttle stop screw 196 which is threadably carried by a projecting bosslike portion 198 of the carburetor body 12. A second arm 280 of lever 188 has an end 202 of linkage 204 (leading as to a related ac celerating pump assembly 205) pivotally secured thereto as well as one end 286 of a coiled torsion spring 208 received within a slot 210 fonned therethrough. The other end 212 of torsion spring 208 is engaged with an abutment 214 formed on the carburetor body 12. Torsion spring 288 serves to resiliently urge the actuating lever 160, through lever 188 and primary throttle shaft 30, in the counter-clockwise direction as viewed in FIG. 5, toward the position as depicted therein.

Lever 188 is also provided with an abutment surface 216 which is adapted to abutingly engage a cooperating stop or abutment portion 218, formed on the carburetor body 12, whenever the actuating lever 161) is sufficiently rotated in the clockwise direction.

A freely rotatable axial spacer-like sleeve 220,

mounted about the primary throttle shaft 30, has a second stronger torsion spring 222 situated thereabout and having ends 224 and 226 projecting therefrom in a manner so as to have spring end 224 resiliently engaging the upper edge of lever arm portion 176 and spring end 226 resiliently engaging the lower edge of lever arm portion 176 (FIGS. 5 and 6). Finally, a third torsion spring 228 is situated generally about the secondary throttle shaft 32 in a manner so as to have a first spring 230 secured to an arm portion of lever 162 and a second spring end 232 resiliently abuttingly engaging a fixed stop or abutment portion 234 carried by the carburetor body 12. As can be seen, torsion spring 228 normally urges lever 162 clockwise toward a position illustrated in FIG. 5.

OPERATION OF THE INVENTION The operation of the invention is generally as follows. First, referring to FIGS. 5, 6 and 7, FIG. 5 illustrates the position the elements assume when the engine is operan'ng at normal temperatures and under curb idle conditions. As the actuating lever 160 is rotated clockwise, so is lever 188 and arm portion 168 of lever 160. After actuating lever 160 has been rotated through, for example, 35 arm 168 engages spring end 226 of torsion spring 222 causing the torsion spring 222 to rotate about the axis of primary throttle shaft 30 and, in so doing, cause the other spring end 224 of torsion spring 222 to transmit such rotational forces to arm portion 176 of lever 170 in order to thereby start the rotation of lever 170 about the axis of primary throttle shaft 38.

Continued clockwise rotation of actuating lever 160 thusly causes further clockwise rotation of lever 170 which, in turn, by means of arm portion 174 and interconnecting linkage 178 results in the counterclockwise rotation of secondary throttle actuating lever 162. Finally, with continued clockwise rotation of actuating lever 168, the various elements and throttle valve 26 and 28 achieve a wide-open throttle position as depicted in FIG. 7.

In view of the above, it can be seen that during conditions of normalengine temperature operation, the relatively strong torsion spring 222 acts as a motion transmitting linkage causing rotation of the otherwise freely joumalled lever 170 after the actuating lever 160 has been rotated some predetermined amount in the throttle-opening direction. During such conditions of normal engine temperature operation, the choke valve 34 and associated linkage means would be in positions as generally illustrated in FIG. 8.

However, let it now be assumed that the engine is shut down and relatively cold so as to have caused the various elements and choke valve 34 to assume positions as depicted in FIG. 2. Once the cold engine is fired and becomes self-sustaining, as is well known in the art, engine or manifold vacuum suddenly increases to a relatively high value and is communicated to the assembly 94 via conduit 98 causing the moveable member 92 to be pulled inwardly toward the assembly 94 to a predetermined stop point. This, in turn, causes linkage 88 to be moved generally towards the right (as viewed in FIG. 2) resulting in lever 72and shaft 68 being rotated clockwise some predetermined degree. Since lever 146 (FIG. 3) is secured to shaft 68 for rotation therewith, the lever 146 causes the choke valve 34 to be forcibly moved (even against the resilient resistance of thermostatic spring 152) some corresponding degree in the opening direction. This is often referred to in the art as being a choke qualifying position.

As the engine temperature increases and the thermostatic element 152 responds thereto, linkage 122 (FIG. 2) is moved generally upwardly causing lever 112 to rotate counter-clockwise which, in turn, through linkage 106, causes lever 72 to be increasingly and progressively rotated in the clockwise direction which rotation cordingly, if during this period of engine operation, the throttle actuating lever 160 is rotated from its position shown in FIG. to its position shown in FIG. 7, the secondary throttle actuating lever 162 will not be permitted to rotate from its FIG. 5 position to its FIG 7 Position.

That is, because of the position of latching lever 126 rotation of the secondary throttle shaft 32 is not permitted. Therefore, at this condition of operation, the relativelystrong coiled torsion spring 222 acts as a lostmotion linkage connection. That is, since latching lever 126 does-not permit rotation of member 136 and shaft 32, rotation of secondary throttle actuating lever 162 will also be not permitted. Accordingly, with secondary throttle lever 162 being maintained in the position shown in FIG. 5, as actuating lever 160 is rotated toward its fully opened position of FIG. 7, arm portion 168 of lever 160, after some predetermined degree of rotation, engages spring end 226 of torsion spring 222 and, upon continued rotation, causes the spring end 226 to resiliently move in a generally unwinding direction with respect to spring end 224 which is being held against movement by arm 176 of lever 170 which, in turn, is now locked against movement by virtue of its connection to secondary throttle lever 162.

In view of the above, it can be seen that the secondary throttle 28 is prevented from experiencing opening movement during the time that the latching lever 126 is in the position as shown in FIG. 2. Further, in the preferred embodiment of the invention, the latching lever 126 remains in the latched position, with respect to abutment member 136, even when the choke valve 34 attains a fully opened position as shown in FIG. 3. However, even after the choke valve 34 attains the fully opened position, the thermostatic means 152 is still effective for experiencing further movement with increasing response to the engine-associated heat. That is, as the thermostatic means 152 continues to unwind, after the choke valve 34 is fully opened, linkage means 122 is progressively moved upwardly causing lever 112 to undergo further rotation until eventually arm portion 118 of lever 112 abuts against a laterally projecting portion 240 carried by latching lever 126 and, in so doing, causes the latching lever 126 to rotate clockwise about its pivot 128 until it finally raises latch arm portion 132 sufficiently high to permit the free passage thereunder of abutment portion 134 of throttle locking member 136 as shown in FIG. 8.

Accordingly, after the thermostatic means 152 has, in response to a predetermined engine temperature, moved the latching lever 126 to the unlatched position the secondary throttle shaft 32 is permitted to be controlled by and positioned in response to the position of the actuating lever 160.

In view of the preceding, it should be apparent that the invention provides means whereby the choke valve can be opened quickly while the opening of the secondary throttle valves can be delayed until after the choke valve is fully opened and a predetermined minimum engine temperature is subsequently attained. This, of course, increases fuel economy while reducing the level of exhaust emission and, at the same time, assuring secondary throttle operation only when the engine has attained sufficient operating temperatures.

Although only one preferred embodiment of the invention has been disclosed and described, it should be apparent that various other embodiments and modifications of the invention are possible within the scope of the appended claims.

I CLAIM:

1. A fuel induction device for an internal carburetion engine, comprising a body, primary and secondary induction passage means formed through said body, primary and secondary throttle valves respectively situated in said primary and secondary induction passages for controlling the flow of motive fluid therethrough, a choke valve pivotally mounted in the primary induction passage upstream of said primary throttle valve, first means including a thermostatic element associated with said choke valve and effective for permitting said choke valve to move from a fully closed cold position to a fully opened position at a first predetermined lower minimum engine temperature, said choke valve being free to open fully against the decreasing resistance of said thermostatic element as engine temperature increases, and said thermostatic element being free to move beyond its choke open position in response to further increasing temperature and second means associated with said secondary throttle valve for preventing said secondary throttle valve from being opened until both said choke valve is fully opened and a predetermined second higher minimum engine temperature is attained subsequent to said choke valve being fully opened, the freedom of said secondary throttle valve to open thereafter being dependent upon said thermostatic element moving beyond its choke open position.

2. A fuel induction device according to claim 1, wherein said primary and secondary throttle valves are respectively mounted for pivotal rotation on primary and secondarythrottle shafts journalled in said body and extending transversely through said primary and secondary induction passages, and wherein said second means comprises latching linkage means operatively connected to said secondary throttle valve.

3. A fuel induction device according to claim 1, wherein said primary and secondary throttle valves are respectively mounted for pivotal rotation on primary and secondary throttle shafts joumalled in said body and extending transversly through said primary and secondary induction passages, wherein said second means comprises latching means operatively connected to said secondary throttle valve, and wherein said first means comprises temperature responsive means responsive to engine temperature and operatively connected to said choke valve.

4. A fuel induction device according to claim 1, wherein said primary and secondary throttle valves are respectively mounted for pivotal rotation on primary and secondary throttle shafts journalled in said body and extending transversely through said primary and secondary induction passages, wherein said second means comprises latching means operatively connected to said secondary throttle valve, and wherein said first means comprises temperature responsive means responsive to engine temperature and operatively connected to said choke valve, said first means also being operatively connected to said latching means so as to be effective for disengaging said latching means after a predetermined engine temperature is attained following said choke valve being moved to a fully opened position.

5. A the] induction device according to claim 1, including primary and secondary actuating levers respectively operatively connected to said primary and second throttle valves, said primary and secondary actuating levers being adapted for rotation with each other, and including lost-motion means operatively connected to said secondary actuating lever, said lostmotion means being to permit rotation of said primary actuating lever during such periods of operation as when said second means is effective for preventing said secondary throttle from being opened.

6. A fuel induction device according to claim 5, wherein said second means comprises latching means operatively connected to said secondary throttle valve, and wherein said first means comprises temperature responsive means responsive to engine temperature and operatively connected to said choke valve.

7. A fuel induction device according to claim 5, wherein said primary and secondary throttle valves are respectively mounted for pivotal rotation on primary and secondary throttle shafts journalled in said body and extending to transversely through said primary and secondary induction passages, wherein said primary actuating lever is fixedly secured to said primary throttle shaft for rotation therewith, wherein said secondary actuatinglever is fixedly secured to said secondary throttle shaft for rotation therewith, and wherein said lostmotion means comprises a portion of motion transmitting linkage means interconnecting said primary and secondary actuating levers.

8. A fuel induction device according to claim 7, wherein said second means comprises latching means operatively connected to said secondary throttle shaft, wherein said first means comprises temperature responsive means responseive .to engine temperature and operatively connected to said choke valve, and wherein said temperature responsive means is operatively connected to said choke valve and to said latching means.

9. A fuel induction device according to claim 8, wherein said latching means comprises a first latching member carried by said secondary throttle shaft for rotation therewith, wherein said latching means comprises a second latching member pivotally carried by said body, and wherein said temperature responsive means is adapted for operative connection to said second latching member for moving said second latching member out of latching engagement with said first latching member whenever said choke valve is fully opened and said predetermined engine temperature has been attained.

10. A fuel induction device according to claim 9, wherein said first latching member includes a first radially extending abutment surface adapted to be angularly swung in accordance with rotation of said secondary throttle shaft, wherein said second latching member includes a second abutment surface adapted to be swung into the path of travel of said first abutment surface whenever said engine temperature is less than said predetermined engine temperature. 

1. A fuel induction device for an internal carburetion engine, comprising a body, primary and secondary induction passage means formed through said body, primary and secondary throttle valves respectively situated in said primary and secondary induction passages for controlling the flow of motive fluid therethrough, a choke valve pivotally mounted in the primary induction passage upstream of said primary throttle valve, first means including a thermostatic element associated with said choke valve and effective for permitting said choke valve to move from a fully closed cold position to a fully opened position at a first predetermined lower minimum engine temperature, said choke valve being free to open fully against the decreasing resistance of said thermostatic element as engine temperature increases, and said thermostatic element being free to move beyond its choke open position in response to further increasing temperature and second means associated with said secondary throttle valve for preventing said secondary throttle valve from being opened until both said choke valve is fully opened and a predetermined second higher minimum engine temperature is attained subsequent to said choke valve being fully opened, the freedom of said secondary throttle valve to open thereafter being dependent upon said thermostatic element moving beyond its choke open position.
 2. A fuel induction device according to claim 1, wherein said primary and secondary throttle valves are respectively mounted for pivotal rotation on primary and secondary throttle shafts journalled in said body and extending transversely through said primary and secondary induction passages, and wherein said second means comprises latching linkage means operatively connected to said secondary throttle valve.
 3. A fuel induction device according to claim 1, wherein said primary and secondary throttle valves are respectively mounted for pivotal rotation on primary and secondary throttle shafts journalled in said body and extending transversly through said primary and secondary induction passages, wherein said second means comprises latching means operatively connected to said secondary throttle valve, and wherein said first means comprises temperature responsive means responsive to engine temperature and operatively connected to said choke valve.
 4. A fuel induction device according to claim 1, wherein said primary and secondary throttle valves are respectively mounted for pivotal rotation on primary and secondary throttle shafts journalled in said body and extending transversely through said primary and secondary induction passages, wherein said second means comprises latching means operatively connected to said secondary throttle valve, and wherein said first means comprises temperature responsive means responsive to engine temperature and operatively connected to said choke valve, said first means also being operatively connected to said latching means so as to be effective for disengaging said latching means after a predetermined engine temperature is attained following said choke valve being moved to a fully opened position.
 5. A fuel induction device according to claim 1, including primary and secondary actuating levers respectively operatively connected to said primary and second throttle valves, said primary and secondary actuating levers being adapted for rotation with each other, and including lost-motion means operatively connected to said secondary actuating lever, said lost-motion means being to permit rotation of said primary actuating lever during such periods of operation as when said second means is effective for preventing said secondary throttle from being opened.
 6. A fuel induction device according to claim 5, wherein said second means comprises latching means operatively connected to said secondary tHrottle valve, and wherein said first means comprises temperature responsive means responsive to engine temperature and operatively connected to said choke valve.
 7. A fuel induction device according to claim 5, wherein said primary and secondary throttle valves are respectively mounted for pivotal rotation on primary and secondary throttle shafts journalled in said body and extending to transversely through said primary and secondary induction passages, wherein said primary actuating lever is fixedly secured to said primary throttle shaft for rotation therewith, wherein said secondary actuating lever is fixedly secured to said secondary throttle shaft for rotation therewith, and wherein said lost-motion means comprises a portion of motion transmitting linkage means interconnecting said primary and secondary actuating levers.
 8. A fuel induction device according to claim 7, wherein said second means comprises latching means operatively connected to said secondary throttle shaft, wherein said first means comprises temperature responsive means responseive to engine temperature and operatively connected to said choke valve, and wherein said temperature responsive means is operatively connected to said choke valve and to said latching means.
 9. A fuel induction device according to claim 8, wherein said latching means comprises a first latching member carried by said secondary throttle shaft for rotation therewith, wherein said latching means comprises a second latching member pivotally carried by said body, and wherein said temperature responsive means is adapted for operative connection to said second latching member for moving said second latching member out of latching engagement with said first latching member whenever said choke valve is fully opened and said predetermined engine temperature has been attained.
 10. A fuel induction device according to claim 9, wherein said first latching member includes a first radially extending abutment surface adapted to be angularly swung in accordance with rotation of said secondary throttle shaft, wherein said second latching member includes a second abutment surface adapted to be swung into the path of travel of said first abutment surface whenever said engine temperature is less than said predetermined engine temperature. 